The present invention relates to a positioning device in which two components -- on being urged towards one another -- abut at an interface and are located in predetermined relative juxtaposition.
When several components are to be connected to one another in predetermined position and when the relative position is to be maintained as accurately as possible, one resorts to a positioning or jointing device of the kind mentioned above. An interface is defined by respective surface portions of two components, which abut against one another to determine their relative position in one of three mutually perpendicular co-ordinates of space. In one known form of such a jointing device, at least one of the components is provided with a positioning recess in the form of a blind cylindrical bore which extends inwardly from the abutment surface. The respective other component is provided with at least one cylindrical pin, which is adapted to enter a respective bore in the first mentioned component. These pins determine the remaining two co-ordinates of the position of the components relative to one another. The components may be urged towards one another by clamping screws, or by similar means. The positioning device should not only determine the relative position in a positive or shape-locking manner on a single occasion but, after disassembling the components and subsequently clamping them together again, reproduce the initial relative position of the components. On the other hand, after the releasing of tightening means of the clamping means, the components should be capable of being separated from one another without appreciable expenditure of effort and without damaging the positioning elements.
In place of the cylindrical pins, it has been known to employ tapering pins. It is disadvantageous in this known device that, for the required accuracy, the skill and effort involved in the prefabrication of the recesses is very great and the narrow tolerances in spite of appropriate effort are often only maintained with difficulty. A plurality of possible faults of such known devices will be considered:
A. The position of the axis of the recess is subject to tolerance. PA1 B. The axis of the bore may not be perpendicular to the interface. PA1 C. The diameter of the bore may vary. The consequence is an inaccurate positioning of the bore being oversize and a wedging and difficulties in disassembly on the bore being undersize. PA1 D. The bore may be non-circular in cross-section. PA1 E. Deviation in the spacing of the recess axes in one or both components.
For the case that more than one positioning location is provided, there is still to be added:
It is an object of the present invention to provide a device in which the positioning accuracy can be increased compared with known devices of generally similar kind without materially increasing and, preferably, decreasing the cost of production and/or the degree of skill involved therein.
For example to eliminate the fault e), one can provisionally tighten together the components in the intended position and then from the outside put in the bores for the fit pins in common operating steps for both components, by which one in the end only still secures the position attained in the setting up of the intended position; in that case, there is not concerned a true positioning device. Moreover, the above stated additional condition is also not fulfilled, namely that the positioning means are to be mountable only from the joint face.
If one in that case employs conical pins in place of the cylindrical pins, then although with certainty one obtains freedom from play and at the same time easier disassembly, it is still impossible just as before to undertake a prefabrication of the bores.
If in place of cylindrical fit pins, one employs longitudinally slotted, hollow-cylindrical spring pins, then the positioning accuracy is worse, while in all cases the assembly (pressing in of the pins) and the disassembly are facilitated.
The principle of the spring-ball detent is also to be mentioned as known device for the positioning of two components in a predetermined relative position, in which a ball movable in a cylindrical bore can under the pressure of a spring project out from the joint surface of a component and for example notch into the conical bore in the contacting joint surface of another component. Apart from the additional effort caused by the accommodation of a spring, this device is not suitable for the set targets already solely for the reason that the mobility of the ball in the cylindrical bore demands a certain play, which in its turn necessarily causes a positioning in accuracy.
Still to be mentioned peripherally are press-stud-like devices, the accuracy of which is however hardly comparable with the above-mentioned device.